Various types of soft magnetic alloys exhibiting high saturation magnetic flux densities have been developed as magnetic core materials for use in transformers, magnetic heads, choke coils or the like in recent years.
For example, Japanese Patent Publication No. 4(1992)-4393 discloses a soft magnetic alloy having the composition represented by the general formula: EQU (Fe.sub.1-a M.sub.a).sub.100-x-y-z-b Cu.sub.x Si.sub.y B.sub.z M'.sub.b
wherein M is Co and/or Ni, M' is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo and a, x, y, z and b satisfy the relationships: 0.ltoreq.a.ltoreq.0.5, 0.1.ltoreq.x.ltoreq.3, 0.ltoreq.y.ltoreq.30, 0.ltoreq.z.ltoreq.25, 5.ltoreq.y+z.ltoreq.30 and 0.1.ltoreq.b.ltoreq.30, PA1 the soft magnetic alloy having a texture, at least 50% of which is composed of fine crystal particles having an average particle size of 1000 .ANG. or less, while the balance is substantially amorphous. The microcrystalline soft magnetic alloy is described as exhibiting low core loss and low magnetostriction. PA1 surface velocity (peripheral surface velocity) of the rotating cooling wheel (R): EQU 10.ltoreq.R.ltoreq.40 (m/sec) (sec=second), PA1 wherein the surface velocity (peripheral surface velocity) of the rotating cooling wheel means the peripheral speed of the rotating cooling wheel which contacts with the molten alloy, and molten alloy injection pressure (P) (gauge): EQU P.ltoreq.0.6 (kgf/cm.sup.2). PA1 surface velocity of the cooling wheel (R): EQU 10.ltoreq.R.ltoreq.40 (m/sec), PA1 casting temperature (Tc): EQU 1150.ltoreq.Tc.ltoreq.1600 (.degree.C.) PA1 molten alloy injection pressure (P) (gauge): EQU P.ltoreq.0.6 (kgf/cm.sup.2), PA1 slot width at the nozzle tip (d): EQU 0.2.ltoreq.d.ltoreq.0.9 (mm), and PA1 gap between the nozzle tip and the cooling wheel (g): EQU 0.05.ltoreq.g.ltoreq.0.3 (mm). PA1 casting temperature (Tc): EQU 1150.ltoreq.Tc.ltoreq.1500 (.degree.C.) PA1 molten alloy injection pressure (P) (gauge): EQU P.ltoreq.0.4 (kgf/cm.sup.2), PA1 slot width at the nozzle tip (d): EQU 0.3.ltoreq.d.ltoreq.0.6 (mm), and PA1 gap between the nozzle tip and the cooling wheel (g): EQU 0.08.ltoreq.g.ltoreq.0.2 (mm).
It is fully described in Japanese Patent Publication No. 4(1992)-4393, Y. Yoshizawa and K. Yamauchi: Journal of the Magnetics Society of Japan, 13, 231 (1989), Y. Yoshizawa and K. Yamauchi: Journal of the Japan Institute of Metals, 53, 241 (1989) and Y. Yoshizawa and K. Yamauchi: Material Science and Engineering, A133, 176 (1991) that, of the microcrystalline soft magnetic alloys having the above composition, those having the composition of the above formula in which, however, M' is at least one element selected from the group consisting of Nb, W, Ta and Mo and a, x, y, z and b satisfy the relationships: a=0, 0.5.ltoreq.x.ltoreq.2, 5.ltoreq.y.ltoreq.20, 5.ltoreq.z.ltoreq.11, 14.ltoreq.y+z.ltoreq.25 and 2.ltoreq.b.ltoreq.5, have not only especially high saturation magnetic flux density as well as low core loss and low magnetostriction values.
The fundamental process for producing the above microcrystalline soft magnetic alloy is disclosed in Japanese Patent Laid-Open Publication No. 3(1991)-219009. The fundamental process comprises the step of quenching a melt having the above composition to thereby form an amorphous alloy and the step of conducting a heat treatment to thereby form fine crystal particles having an average particle size of 1000 .ANG. or less. However, the particulars as to how each of the above steps is performed are not disclosed in the above publication. Further, with respect to the technology for mass-producing an amorphous alloy ribbon as a first step of the production of the microcrystalline soft magnetic alloy ribbon, any practical procedure is not known and it has been believed that the industrial mass-production of an amorphous alloy ribbon suitable for use in the production of the microcrystalline soft magnetic alloy ribbon is difficult.
The inventors have found that, in the production of the amorphous alloy ribbon having the above composition according to the single roll method, it is likely to spontaneously peel from the rotating cooling wheel, as compared with the Fe-Si-B alloy, and further the peel position is irregular, thereby causing the industrial mass-production thereof to be difficult. The irregular position of peel of the ribbon from the cooling wheel causes the ribbon recovery by winding or the like to be difficult, with the result that the productivity of the ribbon is gravely lowered.
For avoiding the above problem, U.S. Pat. No. 3,856,074 proposed a process in which a metal filament formed on the surface of a cooling wheel is held by sandwiching the filament between the cooling wheel and a roller.
On the other hand, U.S. Pat. No. 3,862,658 proposed a process in which the duration of contact of the metal filament with a cooling wheel has been increased either by blowing gas jets against the metal filament formed on the surface of the cooling wheel or by sandwiching the metal filament between a belt or a roller and the cooling wheel.
Further, U.S. Pat. No. 4,202,404 proposed a process in which a metal filament is held by sandwiching the metal filament between a cooling wheel and a flexible belt covering at least 1/3 of the surface of the cooling wheel. The specification of the patent discloses the use of a Cu alloy containing Be as a material of the cooling wheel.
All of the above conventional processes require introduction of special devices, thereby having a disadvantage that the increase in production cost is inevitable.
Moreover, Japanese Patent Laid-Open Publication No. 55(1980)-165261 discloses the use of a cooling wheel composed of, for example, a Cu-Ag alloy which has on its surface a coating of a metal such as Fe or Cr highly wettable with a molten metal, as a means for improving the adhesion between the ribbon and the cooling wheel. This proposal has, however, a drawback in the wear resistance of the cooling wheel and the production cost.